The transmission cooler side is welded to the cooler...it wont turn. If the flare nut isn't frozen, you should be able to get it off with a wrench. If it is frozen, you'll need a new radiator AND a new hose, not that the hose is that big of a deal. You might be able to carefully split the nut with a dremel, but hopefully you won't have to go there. I suspect that if you can find a jam nut that will fit the transmission cooler fitting, you can pack it with teflon or maybe a rubber washer and fix the leak. If it was me, I'd prefer to replace the radiator, as this is probably the first sign of worse trouble coming.

I see no problem with green coolant, but if you post here, you should expect a scolding.